Microfluidic technology has been heralded as a significant technological advance in a number of areas, including biological research, clinical diagnostics, environmental monitoring, pharmaceutical screening, and a variety of others. The advantages associated with this technology are myriad and compelling. For example, the use of small material volumes, digitally controlled fluidics, and sensitive chemistries and detection schemes allows rapid, automatable, reproducible and accurate analytical methods in the above-described areas.
Unfortunately, some of the benefits of microfluidic technology can be difficult to realize. For example, microfluidic systems require only very small amounts of material to perform a given analysis, e.g., in the picoliter to nanoliter range. However, conventional fluid handling technologies, e.g., pipettors, pumps, dispensers and the like, typically are not capable of operating at such small volumes, generally operating above the microliter range. As a result, any advantages of reduced volumes are generally lost in introducing fluids into the microfluidic systems, because larger amounts are dispensed into reservoirs of the device.
One particularly useful method of introducing extremely small volumes of materials into the microfluidic devices is described in U.S. Pat. No. 5,779,868, which describes a pipettor capillary that is integrated with the channels of the microfluidic device. Materials are introduced into the channels of the device by sipping them through the capillary element. Using this improvement, one can readily sample nanoliter and even picoliter volumes of materials into the microfluidic system, thereby realizing this promise of microfluidics.
The present invention generally provides improved devices and methods of fabricating microfluidic systems having such a capillary element.
The present invention generally provides methods of fabricating microfluidic devices that include an external pipettor element having an integrated electrical contact/electrode. The advantages of the present invention are that the electrode is disposed up to the open terminus of the capillary element through a simple fabrication process.
In particular, provided is a method for fabricating a capillary element for electrokinetic transport of materials. The method comprises providing a first capillary element which has a first capillary channel disposed through its length. The capillary channel comprises first and second ends and an outer surface. A continuous layer of an electrically conductive material is applied along a length of the outer surface such that the continuous layer of electrically conductive material extends along the outer surface to a point proximal to, but not up to at least one of the first and second ends. The capillary element is then segmented into at least first and second separate capillary element portions at an intermediate point of the capillary element and the continuous layer. As a result, the first portion of the capillary element comprises the first end and a first intermediate end, and the second portion comprises the second end and a second intermediate end.